Compressor



so as to firmly secure Patented Aug. 4, I953 COMPRESSOR Sylvester M. Schweller, Dayton, Ohio, assignor to General Motors Corporation, corporation of Delaware Dayton, Ohio, at

Application September 6, 1950, Serial No. 183,335

2 Claims.

This invention relates to compressors and particularly to compressors for use in refrigerating systems.

An object of my invention is to provide an improved, simple and inexpensive means or device for adjustably setting the cylinder clearance within a compressor.

Another object of my invention is to provide a compressor piston with an element carried thereby and adjustable relative to the length thereof for increasing and'decreasing the cylinder clearance in the cylinder within which the piston reciprocates.

In carrying out the foregoing objects it is still a further object of my invention to provide a compressor piston with a plug threaded into a bore therein which plug is adjustable relative to the piston to increase or decrease the volume of the compression space in the cylinder within which the piston reciprocates and to provide means for locking the plug in any one of its adjusted positions.

Further objects and advantages of the present invention will be apparent from the following description, referenc being had to theaccompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a fragmentary sectional view of a portion of a compressor showing my improved device set in a position to provide the compressor with a minimum cylinder clearance;

Fig. 2 is a view similar to Fig. 1 showing my device set in a position providing the compressor with increased cylinder clearance; and

Fig. 3 is a fragmentary view taken on the line 3-3 of Fig. 1 showing the top portion of parts of my adjustable cylinder clearance device.

Referring to the drawings, for illustrating the present invention, I have shown in Fig. 1 thereof the working portion of a compressor'such, for example, as a conventional compressor of'a refrigerating system. This portion of the compressor comprises a housing or casing I provided with a. bore ll forming the cylinder of the compressor. A valve plate I 2 is located on top of housing H) to substantially close the upper end of the cylinder II. A head 14 is located on top of plate I2 and suitable bolts I5 extend through holes in a flange provided on head I 4 and through holes provided in plate I2 and these bolts are threaded into tapped holes provided in a flange- I 6 on housing H) as is conventional in the art plate l2 and head 'Mto the housing [0. Gaskets may, if desired, be

2 placed between housing [0 and plate l2 and between plate l2- and head M. The head [4 is provided with a fluid inlet chamber I8 having an inlet port l9 adapted to be connected to the suction conduit or pipe of a closed refrigerating system (not shown). A web 2| on head l4 separates the inlet chamber [8 from a fluid outlet chamber 22 having discharge port 23 adapted to be connected by a pipe to the condenser of the closed refrigerating system. Plate I2 is provided with an opening 26 adapted to permit fluid to enter the cylinder II and with another opening 2'! adapted to permit fluid to escape from the cylinder. These opening 26 and 21 are normally closed by any well known or conventional inlet In the present disclosure I show a fiat spring type inlet valve 28 secured in any suitable or desirable manner, between housing l0 and plate l2, within a recess 29 provided in the lower face of valve plate 12 for normally closing the inlet opening 26. I show a and outlet valves.

flat spring type discharge valve 3| secured in anysuitable and desirable manner, between the plate l2 and head I4, within a recess 32 provided in the upper face of valve plate l2 for normally closing the outlet opening 21. It is to be understood that while the valves 28 and 3| are herein shown more or less diagrammatically they may be of any conventional present day type or design.

A piston 35 having suitable oil grooves therearound and located in the cylinder H is provided with a threaded counterbore or round cavity 36 in its upper closed end into which a disklike plug or element 31 is threaded for a purpose to be hereinafter described. This plug or element 3! is of less thickness than the depth of the counterbore or cavity 36 so as to permit the same to be threaded upwardly or downwardly within the cavity or longitudinally relative to the length of piston 35. The threaded plug or element 3! is provided with a screw driver receiving groove 38 or the like and with a tapped hole 39 which hole receives a set or look screw 49 (see Fig. 3). bearings which connected a pitman or connecting rod 42 in the usual and conventional manner. The lower end of rod 42 is adapted to be connected to an eccentric portion of a shaft of the compressor, which may be rotated by an electric motor, for causing reciprocation of the rod 42 and consequently reciprocation of piston 35 within cylinder H as is well-known and conventional in the art. 7

.In compressors of the type herein illustrated The piston 35 is provided withreceive a wrist pin 4| to which is the cylinder clearance is usually referred to as being the space within cylinder ll intermediate the top of piston 35 and valve plate 12 when the piston is at the uppermost portion of its stroke. By holding this cylinder clearance space to a minimum volume the compressor capacity is at or near its maximum and by increasing this space the compressor capacity is reduced. Stat-ed in another way, if the compressor is designed to have a rather great volumetric cylinder clearance and is driven by an electric motor of predetermined capacity the cylinder clearance of the compressor may be reduced to increase the capacity and efficiency of the compressor, within predetermined limits without overloading and damaging the electric driving motor. Thus to adjustably set the cylinder clearance of the compressor is desirable in order to render the same or similar compressors capable of being installed in different refrigerating systems of like charge, equal evaporator size and driving motor capacity wherein the evaporator of one system may be desired to be maintained at a lower temperature than the evaporator temperature of another system. The adjustable set clearance device incorporated in the compressor herein disclosed permlts accomplishment of the desideratum explained and avoids thenecessity of manufactun ing a great number of compressor sizes for refrigerating systems of different capacities at least within a predetermined capacity range.

After assemblying the piston 36 intothe cylinder ll of the present compressor rotated about the threads on the side wall of cavity 36- to adjust the plug .or element 31 longi tudinally relative to the length of piston 35 to provide a predetermined cylinder clearance within the compressor. thereafter rotated about the threads ofthe tapped hole 39 in plug 3'! to cause the sam to tightly engage the inner or bottom wall of cavity 36 to thereby lock the plug 31 in its adjusted position against rotation relative to the piston. The valve plate l2 and head I l are then secured to the cylinder housing Hi. The adjusted or set position of the adjustable cylinder clearance device may be indicated on an exterior part of the compressor by stamping a numeral or the like insignia thereon. In order to obtain maximum capacity from the compressor the cylinder clearance device is adjusted to and set inthe position thereof disclosed in Fig. l of the drawing. In this position of the plug the compressed fluid remains in the cylinder after the upward or compression stroke. of the piston and this permits down stroke to draw into valve 26, a maximum amount of gaseous refrigerant from chamber 28 and consequently the the iston, during its suctionor suction or low pressure side of the refrigerating system. However if less of the compressor is cylinder clearance device is adjusted, longitudi nally relative to the length of the piston, and set than the full capacity at a point below the top surface thereof such, forexample, as is disclosed in Fig. 2 of the drawing.

In this position of plug 31 a small amount of refrigerant fluid, compressed by a preceding upward or compression stroke of the piston, remains trapped in the cylinder thereby preventing the piston from sucking a great amount of gaseous refrigerant, which it otherwise would be capable of withdrawing, from the suctionor low pressure side of the refrigerating system. Thus, it be obvious that adjustment of plug 31 of the the plug. 3} is The set-screw 40 is- 31 very little if any ofthe cylinder, through desired the plug 3? of the should 4 cylinder clearance device herein disclosed will permit the compressor to meet the requirement of maintaining an evaporator of a refrigerating system between predetermined temperature limits within a range as is desired. A stock of compressors with the different cylinder clearance therein indicated thereon as described will suffice to provide a compressor'of the proper capacity for certain refrigerating system installations and which compressors may be driven by a given size or capacity electric motor without fear of overloading or damaging the motor.

The" adjustable cylinder clearance setting device may'also be changed by a serviceman after installation of the refrigerating system to compensate for certain requirements made of the system. The serviceman may remove the compressor head l4 and valve plate l2 together with valves '28 and 3|, to gain access to the upper end of the piston 35, and may then loosen the lock screw 4.9 to permit rotation or adjustment of plug 31 longitudinally ofthe piston to thereby increase and/or decrease the cylinder clearance within the compressoras desired. Theser-viceman will of courselocl; the plug 3'! in its readjusted position by the lock screw 40 before reassemblying the valve plate l2, valves 28 and 31 and the head l-l upon the compressor.

Inview of the foregoing it should beapparent that I have provided an improved cylinder clearance adjusting device for a compressor by employing a minimum of parts and incorporating the same directly in the compressor piston. The manner in which I lock the plug of the cylinder clearance device insures that the plug will not become loose during reciprocation of the compressor piston; Thecylinder clearance device is located in a position within the compressor normally occupied by a portion of the piston and therefore eliminates the necessity of employing auxilliary equipment adjacent to and outside the compressor while also eliminating the provision of added chambers and'the likewithin the working end of a compressor.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1; In combination, a compressor having a cylinder, a piston therein, and a discharge valve for said cylinder, said piston having an end portion exposed to the interior of said cylinder, a closed end threadedbore in the exposed portion of said piston; a plug threaded into said bore, the outer surface of said plug being normally disposed flush with the exposed end portion of said piston to provide a minimum cylinder clearance within said compresson'said plug, being rotatable into the piston to position its said outer surface inwardly of the exposed end portion of said'piston for increasing the cylinder clearance within said compressor, and a screw threaded through said plug andengaging the closed end of said bore for locking the plug in any one of its adjusted positions against rotation relative to said piston.

2. In combination, a compressor having a cylinder, a piston therein and a discharge valve for said cylinder, said piston havingan endportion exposed to-the interior of said cylinder, a closed endthreaded bore in the exposed portion of said piston, a plug threadedinto said bore, said plug 5 6 cylinder clearance within said compressor, and Number Name Date means threaded through said plug into engage- 1,188,876 Allen June 27, 1916 ment with the closed end of said bore for locking 1,494,764 Wishart May 20, 1924 the plug against rotation relative to said piston. 1,526,244 Shannon Feb. 10, 1925 SYLVESTER M. SCHWELLER. 5 2,148,638 Patterson Feb. 28, 1939 2,160,978 Mock June 6, 1939 References Cited in the file of this patent 2,312,304 Anderson Man 9 UNITED STATES PATENTS 6 3 e h 1949 Number Name Date 977,847 Wright Dec. 6, 1910 10 

